True beef or not true beef? that is the question two volunteers masticating a burger in front of an invited audience in a London theater attempted to answer Aug. 5. Developing this version of the global fast-food staple in a laboratory had taken three months and eaten up £250,000 ($331,400). "It's close to meat," mused the first taster, Hanni Rützler, a nutritional scientist, swallowing with some difficulty. "This is kind of an unnatural experience," confessed the second taster, Josh Schonwald, a writer, as he chewed on history. He meant the lack of ketchup.